June 26, 2013

The day-after effect of brain activation: The brain image at the back presents spontaneous (resting state) patterns before an fMRI-based neurofeedback training session. The front brain image presents spontaneous (resting state) patterns a day after the training session, illustrating the long-term trace of the training. (Credit: Weizmann Institute of Science)

What if experts could dig into the brain, like archaeologists, and uncover the history of past experiences? This ability might reveal what makes each of us a unique individual, and it could enable the objective diagnosis of a wide range of neuropsychological diseases.

New research at the Weizmann Institute hints that such a scenario is within the realm of possibility: It shows that spontaneous waves of neuronal activity in the brain bear the imprints of earlier events for at least 24 hours after the experience has taken place.

Resting waves as “archives”?

The new research stems from earlier findings in the lab of Prof. Rafi Malach of the Institute’s Neurobiology Department and others that the brain never rests, even when its owner is resting.

When a person is resting with closed eyes — that is, no visual stimulus is entering the brain — the normal bursts of nerve cell activity associated with incoming information are replaced by ultra-slow patterns of neuronal activity. Such spontaneous or “resting” waves travel in a highly organized and reproducible manner through the brain’s outer layer — the cortex — and the patterns they create are complex, yet periodic and symmetrical.

Like hieroglyphics, it seemed that these patterns might have some meaning, and research student Tal Harmelech, under the guidance of Malach and Dr. Son Preminger, set out to uncover their significance. Their idea was that the patterns of resting brain waves may constitute “archives” for earlier experiences.

As we add new experiences, the activation of our brain’s networks lead to long-term changes in the links between brain cells, a facility referred to as plasticity. As our experiences become embedded in these connections, they create “expectations” that come into play before we perform any type of mental task, enabling us to anticipate the result.

Recovering traces

The researchers hypothesized that information about earlier experiences would thus be incorporated into the links between networks of nerve cells in the cortex, and these would show up in the brain’s spontaneously emerging wave patterns.

In the experiment, the researchers had volunteers undertake a training exercise that would strongly activate a well-defined network of nerve cells in the frontal lobes. While undergoing scans of their brain activity in the Institute’s functional magnetic resonance imaging (fMRI) scanner, the subjects were asked to imagine a situation in which they had to make rapid decisions.

The subjects received auditory feedback in real time, based on the information obtained directly from their frontal lobe, which indicated the level of neuronal activity in the trained network. This “neurofeedback” strategy proved highly successful in activating the frontal network — a part of the brain that is notoriously difficult to activate under controlled conditions.

To test whether the connections created in the brain during this exercise would leave their traces in the patterns formed by the resting brain waves, the researchers performed fMRI scans on the resting subjects before the exercise, immediately afterward, and 24 hours later.

Their findings, which appeared in the Journal of Neuroscience, showed that the activation of the specific areas in the cortex did indeed remodel the resting brain wave patterns. Surprisingly, the new patterns not only remained the next day, they were significantly strengthened. These observations fit in with the classic learning principles proposed by Donald Hebb in the mid-20th century, in which the co-activation of two linked nerve cells leads to long term strengthening of their link, while activity that is not coordinated weakens this link.

The fMRI images of the resting brain waves showed that brain areas that were activated together during the training sessions exhibited an increase in their functional link a day after the training, while those areas that were deactivated by the training showed a weakened functional connectivity.

A mapping tool

This research suggests a number of future possibilities for exploring the brain. For example, spontaneously emerging brain patterns could be used as a “mapping tool” for unearthing cognitive events from an individual’s recent past.

“Today, we are discovering more and more of the common principles of brain activity, but we have not been able to account for the differences between individuals,” says Malach. “In the future, spontaneous brain patterns could be the key to obtaining unbiased individual profiles.” Such profiles could be especially useful in diagnosing or learning the brain pathologies associated with a wide array of cognitive disabilities.

Comments (10)

“It shows that spontaneous waves of neuronal activity in the brain bear the imprints of earlier events for at least 24 hours after the experience has taken place.” and “This research suggests a number of future possibilities for exploring the brain. For example, spontaneously emerging brain patterns could be used as a “mapping tool” for unearthing cognitive events from an individual’s recent past.”–We are glimpsing right into the future with various research projects in neuroscience, brain imaging, and reverse engineering. Besides the scientific research agenda and curiosity, what do you think, once when the brain “archaeology” becomes reality and the scientists are able to trace one’s brain activities (motivations, memories, thoughts) for the last 24 hours, what this knowledge would be used for? Who would be the most interesting to read someone’s mind in this way? Just curious, who is financing this project now?

Since we remember experiences, and even remember some of our own thoughts, it is obvious that our brain holds “traces” (not a bad word) of what happened in the past. What is novel here is that changes constituting some of those traces can be seen on our instruments, both immediately after and even a day later (pretty amazing).

Recently I listened the true story told by Simon Lewis, the Hollywood producer who underwent the coma condition after the devastating car accident. The details from his story really underlined the point that, perhaps, the brain always functions as some sort of a non-linear clock–a little time machine that connects us with everything–something that was argued from the holographic nature of the brain and the universe. The point being: “the flow of time,” as Simon Lewis referred to, is within the brain and neural activities, and the brain “time machine” works on an “intuitive” level to connect the past experiences with the present strange state, and, who knows, connects directly with the future. I do not know, but I found this article very inspiring. Here is the BBC story link to support my silly thoughts: “My Month in Coma” http://www.bbc.co.uk/i/p019wrl7/

Not sure if everyone realizes that if its just and only “traces” of previous cognitive activity that are detectible, that doesn’t bode well for the idea that you can take a snapshot of the brain that somehow preserves all our previous experiences for future “uploading”. (Aside from the dubious assumption that you can reconstruct experiences because if we see neural pattern x then that “means” experience y).

It would be great if they discover that a large % of these brain patterns are common across individuals. It would then allow for identification and mroe detailed exploration of the unique areas that define individuals. This more detailed analysis could then also be applied to brain emulation and scanning research efforts.

I wonder if they plan to expand this brain activity pattern mapping program to include animals? Animal training programs can be more narrowly defined and closely controlled to imrpove the fidelity and quality factor of measured brain activity responses. I think that might provide some interesting insights…

Honestly, this study sounds like it just discovered dreaming … and maybe more generally learning. Somehow it is not a surprising hypothesis that perhaps “… spontaneously emerging brain activity patterns preserve traces of previous cognitive activity …”.